The invention relates to a reluctance motor electric machine.
The references DE 42 12 547 C2, U.S. Pat. No. 5,266,859, and WO 92/10022 have disclosed electric machines of this kind, which can be operated as reluctance motors. Each electric machine having a respective stator with an essentially annular yoke body, stator pole teeth extending radially inward from this yoke body, and excitation coils associated with the stator pole teeth. Each electric machine having a rotor which is supported so that the rotor can rotate around a rotor axis and has rotor pole teeth that are directed radially outward, which temporarily form pairs with respective stator pole teeth that coincide with them, enclosing an air gap between these respective teeth. There is a minimal reluctance in a pair that is aligned in this manner.
In the reluctance motor according to DE 42 12 547 C2, the rotor has four rotor pole teeth aligned crosswise and the stator has six stator pole teeth aligned at regular angular intervals, wherein the stator pole teeth are each enclosed by an excitation coil winding. By means of its FIG. 1, DE 42 12 547 C2 shows that two respective rotor pole teeth and two stator pole teeth coincide at the same time, which produces simultaneous tensile forces directed radially inward on diametrically opposed stator pole teeth, which leads to an elastic, elliptical deformation of the for example circular ring-shaped yoke body that connects the stator pole teeth to one another. After the excitation coils which produce these tensile forces are switched off and after the disappearance of the magnetic field in these stator pole teeth, the yoke body springs back into its original shape and even beyond this. With rotation of the rotor around one revolution, the yoke body is elliptically deformed six times. The elliptical deformations and their frequency produce annoying noise, which according to the teaching of DE 42 12 547 C2 can be counteracted by reinforcing the yoke body in a manner described in conjunction with FIG. 2 of this reference so that the yoke body is delimited hexagonally on the outside. A reinforcement of this kind increases the natural oscillation frequency of the yoke body or the stator so that with a constant excitation frequency or constant motor speed, the excited oscillation amplitudes are smaller, with the desired result that less noise is generated.
The reluctance motor according to U.S. Pat. No. 5,266,859 likewise has four rotor pole teeth and six stator pole teeth as well as a circular ring-shaped yoke body from which the stator pole teeth protrude radially inward. In order to reduce operating noise, stamped plates, which constitute the rotor and the stator, are twisted like screws in relation to one another and are combined into packets, by means of which the elastic deformations of plates of the stator and/or rotor take place in a time-delayed fashion and there is also a reduction in noise.
The reluctance motor according to WO 92/10022 has a stator with a circular, annular yoke body and ten stator pole teeth leading inward from the yoke body at regular angular intervals. A rotor of this reluctance motor has eight rotor pole teeth and every two of these neighboring rotor pole teeth are combined into pairs which have an angular spacing that corresponds to that of the stator pole teeth. During operation of this reluctance motor, in rotational positions of the rotor which cause minimal reluctance, four air gaps are magnetically flowed through, wherein stator pole teeth disposed diagonally opposite from each other are loaded radially inward in pairs and the yoke ring of the stator therefore receives an essentially elliptical elastic deformation which also causes the generation of noise. The existence of four recurring air gaps is required for a torque delivery of the rotor.